It is well known that machines of this kind can be used either as motors or as generators. The present invention relates to both these alternatives. The following description of an embodiment of a dynamo must be understood as an example for a preferred application of the invention but is not to be understood as a limitation of the scope of the invention.
For generating electrical power to illuminate bicycle lamps, dynamos of various designs are used. In most cases the dynamos are driven by a wheel in frictional contact with a tire of the bicycle. Such dynamos have usually a poor efficiency. The resulting electrical power is low in comparison with the frictional resistance required for driving the dynamo.
An alternative is offered by dynamos mounted in the hub of the wheel. These dynamos are driven by the rotation of the hub. Since the hub offers only limited room for housing a dynamo, this design has been relatively expensive and the corresponding constructions reached only poor efficiency.